Utility vehicles for various purposes such as leisure activities or work, for example, hunting trucks or farming trucks, commonly travel off-road. In utility vehicles equipped with dry brake systems, brake components such as a brake pad and a brake shoe tend to wear out due to adhesion of mud, dust, and other substances, decreasing the life of the brake. In contrast, in utility vehicles equipped with wet brake systems, a brake is accommodated in a case, and is less susceptible to mud, dust, and other substances, increasing its life.
However, the brake systems mounted in the utility vehicles are typically configured so that a brake unit for front wheels and a brake unit for rear wheels operate in association with each other by using, for example, a cable or an oil pressure.
The brake system using the cable is advantageously inexpensive, but requires precision adjustment. The brake system using the oil pressure is disclosed in for example, Japanese Laid-Open Patent Application Publications Nos. 2004-050952 and 2005-207602.
The wet brake system includes a brake mechanism configured to apply a braking force to an axle of the vehicle, and uses lubricating oil or the like to cool the brake mechanism.
The wet brake systems disclosed in Japanese Laid-Open Patent Application Publications Nos. 2004-050952 and 2005-207602, each includes an internal operation lever which is operated via an external operation lever attached coaxially outside a case to directly actuate a brake mechanism.
However, in the above described wet brake systems including the internal and external operation levers, one of the operation levers is exposed to the outside of the case, and therefore, an operating part of the operation lever is susceptible to mud and other substances from a road surface or is likely to be damaged by bouncing stones. In addition, it is necessary to adjust a link mechanism between the external operation lever and a hydraulic cylinder for driving the external operation lever as in the cable, and assembly steps therefore increase.